Tried aggressive strategy going all out - would take him down to 1/2 his HP with stagger - chain break and some soul attack every 3rd (YES THIRD) turn at which point he's immortal... no dmg gotta dispel. Whatever... point his he heals his HP (there goes my advantage), he makes himself immortal and the dude just won't stop pouncing me.
Passive strategy... Sab + Med.... used wound/poison. Poison takes a while to stick... but will eventually. His HP goes down SLOWLY and eventually I die first due to my lack of HP (aka completely wounded).
Teams: Sab + Green Choco Sen + Green Choco Rav + Cloudburst Com + Behemoth (yeah I know he sucks... but takes to long to get another Com and I just want Omega) Sen + Green Choco
Level: 99 in all
With Weapon I got Danjisomething Acc: tried combo of Ribbon, Pure HP, Pure Resist... no luck
I just got done with that a while and had the same problem. Beat the crap out of Caius with Noel but was getting obliterated with Serah. I grabbed a sen and beefed up it's health and won on the first try. Took some time but it was really easy.
Weapon: Indrajit (Dropped by Immortal, +50% ATB) Starting Paradigm: SAB+SEN-W (Pulse Gladiator Lv.28+) Accessories: Magistral Crest, Grimoire Hat
You need speed and sabotage rather than raw power for this fight.
Also, Paradigms MUST be configured for a Wide battle strategy rather than Normal or Cross, as a Wide strategy forces Sarah to use her weapon in bow configuration. Which is critical in this fight as you don't want Sarah getting too close to Caius.
Ignore Auto-Battle. Manual Ability Rotation: Deshell Deprotect Woundga+Wound (Monitor Caius' Max HP with R1 Quick Beastiary ensure it gets to <=30k) Poison
NEVER use MED. Use Potions and on occasion, Wound Potion.
Finish with COM+SEN-W or RAV+SEN-W and in last moments RAV+COM-W or COM+RAV-W or even COM+COM-W.
It may take a try or two to get the right attack pattern to win.
As someone said before, SAB+SEN is going to be your main source of damage. Caius is susceptible to tall of Serah's debuffs, poison being the most important. Basically the paradigms should be all of Serah's roles(except SYN) then a SEN monster. Dispelling Caius's buffs are also helpful.
Check Arthellinus' youtube channel, he has a video guide for this fight sub max level.
He uses Silver Chocobo and Yakshini, start in sen/sen then swap between dual sab/sen paradigms to deshell, poison, and imperil caius. Then swap to com/syn for faith/en buff and back to com/sen for ruin spam. If you are quick you can drop him before chain break. repeat for stage 2, use med/sen to esuna/cure as needed.
"Dear Lord! Bless this ****ing nub, oh Jesus. Bless him right in his stupid face."